Correlation is used in a number of areas, a popular application for correlation is the demodulation of direct sequence spread spectrum data. Correlators used in this application are also referred to as a "matched filter", or sometimes a "passive correlator". The hardware typically consists of a serial sequence of delay elements of width n bits, through which a digitized representation of the baseband signal passes. The width of the delay elements, n, is generally the number of significant bits produced in the sampling process. The juncture or boundaries of the delay elements are referred to as "logic inputs". The logic inputs are assigned positive or negative weights, so as to provide a good match to the code word in use. The output of the correlator is the weighted sum of all or some subset of the logic inputs.
Bruckert describes, in U.S. Pat. No. 3,760,355, a digital pattern detector which is in fact a correlator. The correlator described in U.S. Pat. No. 3,760,355 requires the use of a multi-input accumulator which is capable of assigning different weights to different inputs. The patent also uses a digital representation of the pattern to be matched and does a bit-by-bit comparison. The present invention simplifies the hardware which is required, eliminates the need for the bit-by-bit comparison (and the register storing the pattern), and allows the use of higher than single bit precision.